1. Field of the Invention
The invention generally relates to semiconductor substrate processing systems. More specifically, the invention relates to a method and apparatus for chucking and dechucking a substrate to/from an electrostatic chuck used in a semiconductor substrate processing system.
2. Description of the Background Art
During the manufacture of semiconductor devices, electrostatic chucks provide more uniform clamping and better utilization of the surface of a substrate than mechanical chucks. Electrostatic chucks also can operate in vacuum chambers where the vacuum chucks cannot be used. As such, electrostatic chucks have found wide use in semiconductor substrate processing systems.
Operation of an electrostatic chuck is based on a well-known principle of creating a clamping force-between the biased electrostatic chuck and a substrate (also referred to as a wafer).
Generally, there are two basic configurations of an electrostatic chuck differentiated by the number of the electrodes—unipolar, or monopolar, chucks with one electrode and bipolar chucks with two electrodes. In either configuration, the electrodes are located in proximity to the surface that supports a substrate and embedded in or coated with a dielectric material such as polyimide, alumina, aluminum-nitride and the like.
When electrically biased, these electrodes polarize the material of a substrate and develop a clamping force between the electrostatic chuck and the substrate. Typically, a DC voltage is used in an electrostatic chuck for clamping the substrates during plasma processing. However, AC voltage chucks are known in the art.
A unipolar electrostatic chuck utilizes a plasma or an electrical contact to the substrate to complete a return path for the source of electrical bias, while a bipolar chuck needs only a differential voltage applied across the electrodes to create the clamping force and can operate in a non-plasma environment. In general, the DC voltage employed in an electrostatic chuck is quite high and may reach 700-1500V, however, voltage in a 200-700V range is more common.
When an electrostatic chuck is used in a plasma enhanced semiconductor wafer processing system such as an etch chamber, a physical vapor deposition (PVD) chamber, or a plasma enhanced chemical vapor deposition (PECVD) chamber, or a reactive ion etch (RIE) chamber, the electrode(s) of the chuck draw current from the plasma or source current to the plasma depending on the polarity of the chucking voltage. Such current draw may not be uniform across the wafer and may result in wafer arcing and/or arcing between chamber components. Such arcing may fatally damage the sensitive features on the processed substrates and damage the processing system components.
Therefore, there is a need in the art for a method and apparatus for chucking and dechucking substrates that reduces chamber/wafer arcing.